Motor driven winding mechanism for camera

ABSTRACT

Rotation control of a motor used as a drive source in a motor driven winding-up mechanism for a camera. By rotating the reversible motor in a forward direction, the winding-up transmission mechanism moves. When the film has been wound up by one frame, the reversible motor rotates in the opposite direction a minute angle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to motor driven winding-up mechanisms for camerasand more particularly controls rotation of the motor.

2. Description of the Prior Art

In the conventional motor driven winding-up mechanism for a camera, whenthe film has been wound-up one frame, the stopping member latches thedriving torque transmission system for the sprocket and the takeup spoolso that their rotation is stopped. And, at the same time the currentsupplied to the motor is stopped. With this, however, because theinertia of the motor and transmission system is retained in the form ofstress at the various members of the transmission system and thestopping member, to initiate the next cycle of the winding operation,since the heavy overload lies on the stopping member, the requiredmagnitude of force for releasing the transmission system from thelocking connection is very large. This problem becomes serious when aseries of continuous shots are to be made. If the winding-up stoppingmember is not smoothly moved away from the transmission system, the timeinterval between the successive two shots is randomly varied to a greatextent.

To improve this, a previous proposal is shown in FIG. 5 where anautomatic winding-up unit 102 for a camera 101 includes an electricmotor 103, and gears 104 to 108 constitute a transmission system, whichterminates at a female coupler 109 engaging a male coupler 110 withinthe camera housing. The gears 106 and 107 are connected to each other bya shaft 111 on which are mounted a fly wheel 112 and a coil spring 113.Based on this proposal, at the termination of the winding-up operation,the inertia of the transmission system allows the fly wheel 112 tofurther rotate while charging the spring 113. After the torque of thefly wheel 112 has been balanced with the bias force of the spring 113,it rotates in the reverse direction, whereby the overload on the coupler110 is removed. By this method, however, it takes the fly wheel 112 along time to rest so that when a series of continuous shots is taken, itcannot fully function. Moreover, an alternative problem which isproduced is that the production cost is increased by the increasednumber of parts, and the size of the drive or wind-up unit 102 isincreased.

Another proposal in U.S. Pat. No. 4,182,562 is that after termination ofeach cycle of winding, the motor is over-driven by using a delay meansso that the driving torque transmission and the winding-up stoppingmember are given an excessive load. Then, the reaction of their strainproduces a discouraging effect. However, this method requires that thetransmission system and the stopping member be made of elastic material.Another disadvantage is that with the battery to dropped voltage, thelarge overload is unsolved, or rather intensified.

Also, Japanese Laid-Open Patent Application No. SHO 53-39123 purposesthe use of an electromagnetic clutch to stop rotation of the motor justwhen the winding-up operation terminates resulting in no overload isgiven to the transmission system and the stopping member. This method,however, has the disadvantage that the usable electromagnetic clutch isvery expensive and large.

An object of the present invention is to provide a motor drivenwinding-up mechanism for a camera in which the stress resulting from theinertia of the motor when the winding is completed is removed by verysimple means and low cost. Thereby it is possible to make a series ofcontinuous shots smoothly.

Other objects of the invention will become apparent from the followingdetailed description thereof.

SUMMARY OF THE INVENTION

A motor driven winding-up mechanism for a camera including an electricmotor, a drive circuit for rotating the motor in a winding-up direction,a film winding-up member, a transmitting and driving system fortransmitting rotation of the motor to the film winding-up member,winding-up stopping means for stopping rotation of the motor and thetransmitting and driving system each time a film has been wound up by aprescribed number of frames, and backward motion driving means fordriving at least the transmitting and driving system to rotate to a fewdegrees of angle in the reversed direction to that in which it rotatedwhen in winding at a time after the film has been wound up by theprescribed frame and before the initiation of the next film framewinding operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a driving torque transmission system ina camera having a motor driven winding-up mechanism according to thepresent invention.

FIG. 2 is an electrical circuit diagram of a control circuit of thereversible motor of FIG. 1.

FIGS. 3(a) and 3(b) are pulse timing charts illustrating the manner inwhich the circuit of FIG. 2 operates.

FIGS. 4(a) to 4(d) are elevational views of the winding-up stoppingmeans in different operative positions.

FIG. 5 is a sectional view of the combined main parts of theconventional automatic winding-up unit and the camera.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will next be described by reference to thedrawings.

In FIG. 1 there is shown one embodiment of a motor driven winding-upmechanism according to the present invention in which a reversible motorM which can change the direction of rotation between forward and reversedepending on the direction of flow of driving current thereto, has anoutput shaft 1a on which is fixedly mounted a pinion gear 2. A geartrain 3, a planetary gear mechanism 4 capable of selectively cooperatingwith a gear 5 and a film rewinding gear train 15 depend on the forwardand reverse directions of rotation of the motor 1 respectively, and agear 7 fixedly mounted on a common shaft 6 of the gear 5, constitute adriving torque transmission system. A cam disc 8 is coaxially fixedlymounted on the upper surface of the gear 7 and rotates one revolutionfor each film winding frame. Formed in the peripheral surface of thiscam disc 8 is a cutout 8a and the cam 8 displacement is synchronizedwith the termination of each winding cycle. A swingable winding-upstopping lever 9 is urged by a spring 20 so that its one end or probeportion 9a always abuts the periphery of the cam disc 8. When the probe9a drops in the cutout 8a, the lever 9 turns clockwise. When a shutterrelease is actuated, on the other hand, as the mirror moves upward, areturn control lever 25 moves while turning the lever 9 in acounter-clockwise direction. A switch 30 for detecting when the windingis completed is adjacent to the winding stop lever 9 and is closed whenthe winding operation is in progress, and is to open when it isterminated. A sprocket 10 having teeth 10c for engagement in theperforations of the film is fixedly mounted on a common shaft of a gear10a which meshes with the gear 7. Another gear 10b is drivinglyconnected through an intermediate gear 11 to a spool gear 12. Rotationof the spool gear 12 is transmitted through a friction mechanism 13 to atakeup spool 14 on which the film is wound up. Reference numeral 15identifies a film rewinding transmission gear train.

FIG. 2 illustrates a control circuit for the reversible motor M in anembodiment of the present invention. Reference numerals R1-R8 identifyresistors; a switch SW1 responsive to a stroke on a release button (notshown); switch SW2 is controlled by the switch 30 of FIG. 1 and a signalfrom a circuit (not shown) for controlling the trailing curtain of theshutter so that when the trailing curtain has run down, it closes, andwhen the winding is completed, it opens in time with the opening of theswitch 30. Reference symbol Mg identifies a release start magnetreference symbols OS1 and OS2 identify mono-stable multivibrators. Themultivibrator OS1 produces a pulse of very short duration necessary tocheck the current supply at the time of release, and the multivibratorOS2 produces a pulse of a duration necessary to activate the releasestart magnet Mg; I1-I4 identify inverters; COM identifies a comparator;M the reversible motor M of FIG. 1; Q1-Q5 transistors; E an electricalpower source or battery; AND an AND gate; V1 a constant voltage source;and FF identifies a D type flip-flop.

The operation of the mechanism of FIG. 1 and the circuit of FIG. 2 arenext described by reference to the pulse timing charts of FIGS. 3(a) and3(b) and the operative positions of the essential parts to an enlargedscale in FIGS. 4(a) to 4(d).

When the switch SW1 is closed in response to actuation of a camerarelease, a signal that rises from L to H is applied to the inputterminal of the mono-stable multivibrator OS1, whereby a pulse which ismaintained at H for a prescribed time is produced from the mono-stablemultivibrator OS1. This pulse signal H is then applied to the base ofthe transistor Q2 while the base of the transistor Q3 is supplied with asignal L through the inverter I2. Since the transistors Q2 and Q3 areON, the reversible motor M is supplied with current flowing in adirection indicated by i2. Thus, the motor M rotates in directionopposite to the winding-up direction. It should be pointed out that thisbackward rotation of the motor M operates only for a very short timeequal to the width of the pulse from the mono-stable multivibrator OS1.

Meanwhile, the pulse signal H from the aforesaid mono-stablemultivibrator OS1 is applied through the inverter I3 to a clock inputterminal CLK of the D type flip-flop FF. In time with the change oflevel of the pulse signal from H to L, or, for the clock input terminalCLK, the rise from L to H, the output signal from the comparator COM asapplied to a data input terminal D is latched. Since an actual volage VEof the battery E after having been divided by the resistors R1 and R2 toa value: ##EQU1## is applied to the non-inverting input terminal of thecomparator COM, and a reference voltage VREF from the constant voltagesource V1 is applied to the inverting input terminal thereof, the outputof the comparator COM reaches H level when ##EQU2## and L level when##EQU3## It is to be noted here that the value of the reference voltageVREF is determined to assure the reliability of exposure control withthe accompaniment of the release operation and control of movement ofthe shutter curtains, and, therefore that when the condition ##EQU4## issatisfied, or the comparator COM produces the signal H, the photographicoperation is normal. When ##EQU5## the battery E must be replaced.

Now assuming that the voltage of the battery E is so high that thecomparator COM produces an H level output signal as shown in FIG. 3(a),the condition ##EQU6## is satisfied. Having latched this signal, the Dtype flip-flop FF changes its Q output to an H level. This output isapplied to one input terminal of the AND gate AND. Since the output ofthe mono-stable multivibrator OS2, which is applied to the other inputof the AND gate AND rises in synchronization with the aforesaid latchingoperation, the AND gate AND then produces an output of the same waveformas that of the output of the mono-stable multivibrator OS2. By thispulse signal H from the AND gate AND, the transistor Q5 is turned on theenergize to release start magnet Mg. After that, the various mechanismsof the camera operate in sequence to release the shutter. Note, with theswitch SW1 continuously closed, its output takes an H levelintermittently as the ON-to-OFF operation of the switch SW2 is recycled.This results in automatically making a series of continuous shots.

Alternatively, assuming that as the voltage of the battery E becomeslow, ##EQU7## results, then the comparator COM produces an L leveloutput signal, as shown in FIG. 3(b). Having latched this signal, the Dtype flip-flop FF gives its Q output of L level to the AND gate AND.Therefore, the output of the AND gate AND is maintained at an L level,preventing the release start magnet Mg from being actuated.

Therefore, only when the voltage of the battery E is sufficiently high,a sequence of operations to a shutter release can be carried out. Nextthe winding operation that follows the termination of the releaseoperation will be explained by reference to FIG. 3(a). That is, as therelease operation nears the terminal end, when the trailing curtain ofthe shutter runs down, the switch SW2 is closed. In response to this,the inverter I1 produces an L level output which is then applied to thebase of transistor Q1, thereby the transistor Q1 is turned on, while theoutput of the switch SW2 is applied to the base of the transistor Q4whereby the transistor Q4 too is turned on. Therefore, the reversiblemotor M is supplied with current flowing in another direction i1,rotating forward. This forward rotation of the motor M continues untilthe switch SW2 is opened as the film is advanced one frame, sensed bythe switch 30 of FIG. 1.

Operation of the winding-up transmission system based on the operationof the reversible motor M will be first explained in connection with theforward rotation of the reversible motor M for the purpose of betterunderstanding. That is, as the releasing operation goes on, when themirror (of the single lens reflex camera) moves upward, the returncontrol lever 25 moves in a direction indicated by arrow A in FIG. 4(a),thereby the winding stop lever 9 is turned in a counterclockwisedirection, and the probe 9a is disengaged from the cutout 8a of the camdisc 8. Such counterclockwise movement of the stop lever 9 also causesclosure of the switch 30. And, in the next step of the releasingoperation, the return control lever 25 moves backward or in a directionindicated by arrow B in FIG. 4(b), allowing a later clockwise movementof the stop lever 9. When the releasing operation reaches the finalstep, or the trailing curtain of the shutter has run down, the switchSW2 is closed, causing the reversible motor M to rotate in thewinding-up direction. Rotation of the motor M is transmitted through thepinion gear 2, the gear train 3, the planetary gear mechanism 4, theshift gears 5 and 7, the gear 10a, the sprocket 10, the gear 10b, thegear 11, and the spool gear 12 in this order to the spool 14 to take upthe advanced film thereon. During this winding-up operation, the camdisc 8 also rotates. When the film is advanced one frame, the probe 9aof the winding-up stop lever 9 then drops in the cutout 8a. As thiswinding-up stop lever 9 turns in the clockwise direction, the switch 30opens itself, and also the switch SW2. Thus, one cycle of the filmwinding operation is completed. It should be recognized here that justafter the motor M has been de-energized, a constraining force is exertedbetween the probe 9a of the winding-up stop lever 9 and the cutout 8a ofthe cam disc 8 by the inertia of the over-running motor M and thevarious gears of the transmission system. If this constraining force isretained, a large force would be necessary to turn the winding-up stoplever 9 in the counterclockwise direction when the cam disc 8 isreleased from latching connection therewith.

According to the present invention, however, when making the next shot,depression of the release button closes the SW1 switch which in turncauses the mono-stable multivibrator OS1 to energize the reversiblemotor M for a very short time equal to the width of the pulse producedtherefrom before initiation of actual photography (the leading curtainof the shutter runs down). The motor M rotates a minute angle backwardalong with the cam disc 8 from the position of FIG. 4(c) to a positionof FIG. 4(d) where the winding-up stop lever 9 is released from theclamping connection with the cutout 8a. This provides assurance thatconsiderably reduced power of the return control lever 25 suffices forcontrolling the counterclockwise movement of the winding-up stop lever 9accurately and reliably.

In the embodiment, the planetary gear mechanism 4 is used as a part ofthe transmission system. Therefore, excessive backward rotation of themotor M brings the planetary gear into engagement with the rewindingtransmission gear train 15, as it revolves around the sun gear. It istherefore understood that not only the stress of the transmission systemis immediately released after termination of each cycle of winding butthere is also no possibility of bringing the opposite shoulder of thecutout 8a into bracing engagement with the probe 9a of the winding-upstop lever 9.

Note, even without the use of the planetary gear mechanism 4 in thetransmission system, it is needless to say that an equivalent effect canbe obtained because the strain-clamping force is loosened by thebackward rotation of the motor M, if the amount of backward rotation isadjusted with great accuracy.

It will be appreciated from the illustrated embodiment that the stressof the sprocket control mechanism (the winding-up stop lever 9 and thecam disc 8) has constituted a problem with cameras having theconventional motor driven winding-up mechanism which is released withoutemploying a new mechanical part. In a simple method the reversible motorM is rotated backward to a small angle after the stoppage of all themembers of the winding-up mechanism that follows winding completion. Bythis feature of the invention it is possible not only to smoothlyoperate the sprocket control mechanism but also to insure that whenmaking a series of continuous shots, the time interval between thesuccessive shots can be accurately controlled.

It is to be noted that in this embodiment, whether or not the actualvoltage of the electrical power source or battery E is above asatisfactory level for each operation to release the shutter is checkedin coincidence with the releasing of the stress described above. Sinceno time space the voltage checking solely occupies is not introducedinto the sequence of operations of the camera, the minimum time gapbetween the successive two shots can be shortened.

Though the foregoing embodiment has been described as the one-frameadvance control means taking the form of the winding-up stop member (thecombination of the lever 9 and the cam disc 8), another form, forexample, an electrically operated braking mechanism may be employed sothat the stoppage of the sprocket is controlled only electrically.

Also though in the above-described embodiment the backward motionimparting means for rotating the transmission system backward to a smallangle each time the film has been advanced one frame is formed byreversing the rotation of the motor as the winding-up power source,another method, for example, by using an additional motor solely usedfor film rewinding, may be used. In this case, this rewinding motor isrotated in a rewinding direction to a small angle each time the windingis completed.

Also, in the invention, the winding-up stopping means is not necessarilyoperated for every one frame, but another embodiment in which thestopping means is actuated after two or more frames have been advancedis also possible to obtain an equivalent effect to that in theabove-described embodiment.

As has been described above, the present invention provides thepossibility of smooth continuity of motorized shootings by removing thestress that has been introduced by the inertia of the motor and thetorque transmission system when the winding operation is completed insuch a way that for every one frame of film to be advanced, after thepreceding cycle of energization of the motor for driving the torquetransmission system was terminated, said transmission system is turnedbackward to a small angle by the backward motion driving means.

As compared with the prior known methods of removing the stress,therefore, the use of means of low cost and simple structure makes itpossible to provide a motor driven winding-up mechanism for a camera ofremarkably improved capabilities.

What is claimed is:
 1. A motor driven winding-up mechanism for a cameracomprising:(a) an electric motor; (b) a drive circuit for rotating saidmotor in a winding-up direction; (c) a film winding-up member; (d) atransmitting and driving system for transmitting rotation of said motorto said film winding-up member; (e) winding-up stopping means forstopping rotation of said motor and said transmitting and driving systemeach time a film has been wound up by a prescribed number of frames; and(f) backward motion driving means for driving at least said transmittingand driving system to rotate to a few degrees of angle in the reverseddirection to that in which it rotated when in winding at a time afterthe film has been wound up by the prescribed frame and before theinitiation of the next film frame winding operation.
 2. The mechanismaccording to claim 1, whereinsaid winding-up stopping means includes arotary cam having a cam displacement formed in a stopped position as itmoves along with said transmitting and driving system, and a windingstop lever slidingly contacting with said rotary cam.
 3. The mechanismaccording to claim 1, whereinsaid backward motion driving means isoperated each time the winding of film by one frame is completed.
 4. Themechanism according to claim 1, further comprising:(g) voltage detectingmeans for detecting the voltage of an electrical power source or batteryof the camera.
 5. The mechanism according to claim 4, whereinthe voltagedetection by said voltage detecting means is made carried out when saidbackward motion driving means is operated.
 6. The mechanism according toclaim 1, whereinthe operation of said backward motion driving means iscarried out in the early stage of a releasing operation.
 7. A motordriven winding-up mechanism for a camera comprising:(a) a reversiblemotor; (b) a drive circuit for rotating said reversible motor in awinding direction; (c) a film winding-up member; (d) a transmitting anddriving system for transmitting rotation of said motor to said filmwinding-up member; (e) winding-up stopping means for stopping rotationof said motor and said transmitting and driving system each time a filmhas been wound up by a prescribed number of frames; and (f) backwardmotion driving means for rotating said reversible motor to a few degreesof angle in a reversed direction to that when in winding up at a timefrom the moment at which a film has been stopped from advancing throughthe length of a preset number of frames until the initiation of windingup of the next frame.
 8. The mechanism according to claim 7, whereinsaidwinding-up stopping means includes a rotary cam having a camdisplacement formed in a stopped position as it moves along with saidtransmitting and driving system, and a winding stop lever slidinglycontacting with said rotary cam.
 9. The mechanism according to claim 7,whereinsaid backward motion driving means is operated each time thewinding of film by one frame is completed.
 10. The mechanism accordingto claim 7, further comprising:(g) a clutch provided at an intermediatepoint in said transmitting and driving system and operating to connectall said transmitting and driving system when said reversible motorrotates in a winding direction; and (h) a film rewind driving systemarranged to connect with said clutch when said reversible motor isrotated in a reversed direction to that when in winding up.
 11. Themechanism according to claim 10, whereinsaid clutch is made to be aplanetary clutch.